Agridable

Bugfix for in-package JS/CSS imports

Needed to add JS/CSS files to build of python package. Did this by:

- Adding MANIFEST.in file
- Adding include_package_data=True to setup.py
- Added init.py to /assets folder
- Updated readme.md

Incorporated JS and CSS files into the package directly via the main __init__.py.

Many thanks to RenaudLN for the tip!

The first working release of AGridable 🙌